external/openssh: update to 6.8p1.

In preparation for some updates to external/openssh to make it work with
BoringSSL, this change updates the code to a recent version. The current
version (5.9p1) is coming up on four years old now.

  * Confirmed that f5c67b478bef9992de9e9ec91ce10af4f6205e0d matches
    OpenSSH 5.9p1 exactly (save for the removal of the scard
    subdirectory).

  * Downloaded openssh-6.8p1.tar.gz (SHA256:
    3ff64ce73ee124480b5bf767b9830d7d3c03bbcb6abe716b78f0192c37ce160e)
    and verified with PGP signature. (I've verified Damien's key in
    person previously.)

  * Applied changes between f5c67b478bef9992de9e9ec91ce10af4f6205e0d and
    OpenSSH 5.9p1 to 6.8p1 and updated the build as best I can. The
    ugliest change is probably the duplication of umac.c to umac128.c
    because Android conditionally compiles that file twice. See the
    comment in those files.

Change-Id: I63cb07a8118afb5a377f116087a0882914cea486
diff --git a/sftp-common.h b/sftp-common.h
index 9ed86c0..2e778a9 100644
--- a/sftp-common.h
+++ b/sftp-common.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-common.h,v 1.11 2010/01/13 01:40:16 djm Exp $ */
+/* $OpenBSD: sftp-common.h,v 1.12 2015/01/14 13:54:13 djm Exp $ */
 
 /*
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -28,6 +28,7 @@
 /* Maximum packet that we are willing to send/accept */
 #define SFTP_MAX_MSG_LENGTH	(256 * 1024)
 
+struct sshbuf;
 typedef struct Attrib Attrib;
 
 /* File attributes */
@@ -44,8 +45,8 @@
 void	 attrib_clear(Attrib *);
 void	 stat_to_attrib(const struct stat *, Attrib *);
 void	 attrib_to_stat(const Attrib *, struct stat *);
-Attrib	*decode_attrib(Buffer *);
-void	 encode_attrib(Buffer *, const Attrib *);
+int	 decode_attrib(struct sshbuf *, Attrib *);
+int	 encode_attrib(struct sshbuf *, const Attrib *);
 char	*ls_file(const char *, const struct stat *, int, int);
 
 const char *fx2txt(int);